The main purpose of tantalum, as a metal powder, is to make electronic components. Usually, many enterprises recycling tantalum capacitors will sell the recovered tantalum to tantalum processing plants for reuse. Common USES include capacitors and some high power resistors. Tantalum capacitors account for more than 90% of all tantalum USES. No matter it is a large scientific computer or a small electronic instrument, tantalum capacitors can be found everywhere, which is also the most important use of tantalum.
At the same time, tantalum resources are relatively scarce, which determines that tantalum mining in the world has a history of bloody conflicts. In Africa, the discovery of tantalum ore is the starting point for a scramble or even a brawl over its economic value that has killed an estimated 5.4 million people since 1998. This has made tantalum the deadliest flashpoint for regional conflicts in the world since world war ii. Armed conflict zones in the Congo basin continue today because of resource exploitation. In the future, these conflicts may persist.
The microstructure of pure tantalum nanosheet was characterized by electron backscattering diffraction (SRD) and transmission electron microscopy (tem). The mechanical properties of nano-sheet were characterized by hardness test, tensile test and nano-indentation test. The influence of processing technology and microstructure on the thermal stability of nanometer sheet was studied. The results show that the orientation difference of small Angle grain boundary of pure tantalum deformed microstructure after 4 ECAP deformations increases continuously during the rolling process, which leads to the increase of large Angle grain boundary fraction. After 8 passes of ECAP deformation, the large Angle grain boundary fraction of pure tantalum deformed microstructure is saturated, and the significant increase of texture strength in the subsequent rolling process leads to the continuous decrease of the large Angle grain boundary fraction. The results show that the monolithic nano-sheet pure tantalum prepared by the unidirectional rolling process with 8-pass a-mode ECAP deformation at the composite liquid nitrogen temperature has the smallest sheet width. With the increase of rolling reduction, the width of the nanosheet layer was continuously refined, and the width of the nanosheet layer was even refined to about 43nm when the rolling reduction was 90%. However, there is a certain deviation between the sheet width of pure tantalum and the theoretical value in the rolling process. When the rolling reduction is small, dislocation proliferation, plugging and entanglement form dislocation cell structure, contributing to additional refining effect, resulting in sheet width less than the theoretical value; When the rolling reduction is large, the effect of recovery plays a leading role in the width of the nanosheet, resulting in the actual width of the nanosheet being higher than the theoretical predicted value. The yield strength and microhardness of pure tantalum increase with the decrease of the width of nano-sheet, while the fracture elongation and strain rate sensitivity index decrease with the decrease of the width of nano-sheet.
